The invention relates to a fuel filter assembly having electrically conductive features and more particularly to a fuel filter assembly having an electrically conductive spring which electrically connects electrically conductive filter components disposed within a housing with a conductive pin extending through the housing.
For many years, fuel filters in motor vehicles comprised a filter element disposed within a metallic housing at a convenient location in the fuel line, often times in the engine compartment. While hoses to and from the housing were generally rubber and thus non-conductive, the housing was metal and was secured to a component or panel of the automobile and was thus grounded. Accordingly, any electrostatic charge generated by passage of fuel through the filtration element was readily and safely grounded through the filter housing to the motor vehicle body.
The constant study of vehicle weight directed to weight reduction as well as continuing development of plastics and polymers has affected the fuel delivery and filtration systems of vehicles as it has nearly every vehicle system and component. Rather than metal, filter housings are now frequently fabricated of a fuel tolerant plastic such as nylon. Such a construction results in the filtration element being electrically insulated from the vehicle ground. An electrostatic discharge (ESD) may result as electrostatic charge in the filtration element increases as a result of fuel flow therethrough. Frequently, such discharges occur through the housing to the most proximate metallic vehicle body feature. Repeated discharge can result in leakage through the filter housing which is unacceptable.
In response to this problem, filtration devices have been developed which seek to eliminate electrostatic discharges and their consequences by providing a drainage path to ground which prevents build up of an electrostatic charge.
For example, U.S. Pat. No. 4,187,179 discloses an electrically conducting spring in a swimming pool filter having a plurality of non-conductive filtration cartridges. The filtration cartridges are mounted upon a conductive end plate and a plurality of electrically conducting resilient leaf springs contact an outer conductive housing and drain static charges from the plate.
U.S. Pat. No. 4,999,108 teaches a fuel filtration device having a perforated metal cylinder with inner and outer filter elements. The cylinder is in contact with a wire in an end plate which communicates with a conductive mounting stud.
U.S. Pat. No. 5,382,351 discloses plating a filter housing, inside and out, with a conductive material such as chromium, nickel or copper by vacuum metalization or sputtering.
U.S. Pat. No. 5,584,987 teaches a fluid filter configuration in which a compression spring retains and biases a filter element toward one end of the housing.
U.S. Pat. No. 5,898,560 discloses a filter having a conductive housing with an electrically conductive member and means for converting laminar flow to turbulent flow.
U.S. Pat. No. 6,168,713 also discloses a filter assembly having a conductive path for draining an electrostatic charge to ground.
The foregoing six United States Patents are directed to the above-referenced difficulty and it is therefore apparent that fuel filtration devices directed to minimizing or eliminating the problem of electrostatic discharge are highly desirable.
A fuel filter includes features adapted to collect and drain static electrical charges occasioned by the passage of fuel therethrough. The filter includes a two-piece plastic housing having an end cap and a cylindrical portion with an end defining inlet and outlet fittings. The filter element is cylindrical and includes an outer perforated metal shell, an intermediate pleated paper filter and an inner perforated metal shell. Both metal shells are secured and electrically coupled to an electrically conductive end cap. The conductive end cap is electrically and mechanically connected to a conductive, circular spring. A portion of the spring engages a conductive pin which extends through the cylindrical portion of the housing and may be connected to a suitable ground to drain off static electrical charges generated by fuel flowing through the filter. The other end of the filter element is either embedded in the housing end cap or, in an alternate embodiment, a smaller end cap which is received in the housing end cap.
It is thus an object of the present invention to provide a fuel filter assembly intended to minimize electrostatic discharge.
It is a further object of the present invention to provide a fuel filter assembly having a filtration element surrounded by inner and outer conductive elements.
It is a still further object of the present invention to provide a fuel filter assembly having a pleated paper filter surrounded by conductive metal elements.
It is a still further object of the present invention to provide a fuel filter assembly having conductive elements which cooperate with a conductive spring and pin to drain off electrostatic charges from fuel passing therethrough.
It is a still further object of the present invention to provide a fuel filter assembly and housing wherein a conductive metal surround, a conductive end cap, a conductive spring and a conductive pin define an electrical path to the exterior of the housing to drain off electrostatic charges resulting from fuel filtration.
Further objects and advantages of the present invention will become apparent by reference to the following description of the preferred embodiment and appended drawings wherein like reference numbers refer to the same component, element or feature.